The present invention relates to an automatic recording current controller when two different signals are double recorded in the deep portion and surface portion of a magnetic recording medium in a magnetic recorder (containing also a magnetic recorder/reproducer) such as a video tape recorder (VTR), MTR, or a data recorder (magnetic recording media are not limited to tape media).
For example, a video tape recorder (VTR) for recording a high-fidelity audio signal in the deep portion of a magnetic tape of a magnetic recording medium and for recording a video signal overlapping the audio signal in the surface portion thereof, is known as a magnetic recorder capable of double recording.
Generally, in such a conventional VTR, when video and audio signals are recorded, the setup optimum recording level is referenced for controlling the recording current of the video signal.
An auto calibration device (automatic recording current controller) for automatically adjusting the recording level of a video signal recorded in the surface portion of a magnetic tape to an optimum value in double magnetic recording in such a VTR is described, for example, in Japanese Patent Unexamined Publication No. Hei 5-197907.
This device relates to a VTR which records an audio signal at a given level in the deep portion of a magnetic tape, then records a video signal, whose level changes step-wise, in the surface portion so as to overlap the audio signal. The recording level Wa of the video signal when the level of the video signal reproduced from the magnetic tape reaches the maximum, is stored in a storage. Also, the recording level Wb of the video signal when the level of the reproduced audio signal exceeds a preset reference value, is stored in the storage. When Wa.ltoreq.Wb, Wa is adopted as the optimum recording level; when Wa&gt;Wb, if Wb lies within a predetermined range with respect to Wa, Wb is adopted as the optimum recording level; when Wb is outside the predetermined range, the level nearest to Wb in the predetermined range is adopted as the optimum recording level.
By the way, even if such a conventional automatic recording current controller attempts to determine the predetermined range with respect to the recording level Wa and place the reproduced video signal level in an allowable range, it is impossible to precisely control the video signal recording level. This can be explained in the following example:
The reproduced video signal level with respect to the recorded video signal level varies depending on the type of a magnetic tape used or degradation of the recording/reproducing characteristic of the tape.
Since the predetermined range is determined for the video signal recording level Wa when the reproduced video signal level reaches the maximum, even if the video signal recording level is the same value in the predetermined range, the reproduced video signal level may vary, whereby the picture quality of an image provided by the reproduced video signal may be impaired.